Energy cost calculator
Calculation of energy cost per gigajoule (GJ)
Use this page to calculate and compare the cost of heating energy from a
number of different fuels.
It is set up for firewood, coal, oil, LPG gas and electricity as fuels.
Prices vary from place to place and time to time, and we must expect the price
of petroleum to rise more-or-less continuously for the foreseeable future.
This page was created on 2005/05/08
(May 8th 2005); modified 2008/11/09
Contact: email email@example.com
In the Mid-North of South Australia in May 2005 I calculated the
approximate energy costs, in Australian dollars (Au$1 ~ US$0.75), shown on
the table at the right.
The per gigajoule costs shown in this box were based on what seemed the most
reliable prices I was able to find at the time.
|Fuel||Fuel price||Cost per GJ
|Brown coal briquettes||$350/tonne||$16
|Compressed natural gas (CNG)||$16.95/GJ||$17*
|Liquified petroeum gas (LPG)||$0.54/Litre||$21
|*A substantial supply charge also had to be
paid for connection to the CNG and electricity supply systems.
As the peak of oil production is approached and passed, we must expect
the price of oil and LPG to rise.
As governments begin to take
(and global dimming and
seriously, coal will become scarcer and more expensive.
Electricity, especially in Australia, is commonly generated by
burning fossil fuels; this is obviously unsustainable from several points of
Electricity is more efficient for heating than the calculated cost indicates
because no heat goes up the flew, unlike those fuels that are burned.
Also, if it powers a reverse cycle air conditioner its efficiency can be
See my page
Considering the above factors,
Firewood will probably become more
important as a fuel in the Western World in future.
Firewood generally needs to be chopped into smaller pieces than those
that you will get from the wood merchant. This might be thought of as a
disadvantage or as a useful source of exercise.
Coal also requires manual handling.
All the fossil fuels add to the
problem when burned. Using
electricity might also add to greenhouse depending on how your
electricity is generated.
Europeans and others who do not use the dollar can simply enter prices
in their own monetary unit; the answers will be in the same units.
For USAzians who do not use metric units I can only say: learn metric
and move into the twentieth century (I would say the twenty-first century, but
it would be safer for you to move a small step at a time).
Some energy units, conversions and definitions are given on my
Energy Units page.
The calculation of the energy cost from firewood assumes that the firewood is
air-seasoned (that is, it had been dried by allowing air to freely circulate
around it for long enough to remove most of the moisture). Air-seasoned wood
releases about 16GJ/tonne when burned; see
For comparison, green wood releases about 10GJ/t, oven-dry wood 20GJ/t
(Clean Energy Future Report
by the Clean Energy Future Group.)
Please note that the energy content of coal can vary greatly. If your coal
has an energy content very different from the figure that you enter then
the calculated energy cost will be wrong to the same extent. The moisture
content of the coal will also effect its energy content. Some coal has an
energy content as low as 15GJ/tonne.
The calculation works on the energy in a litre of heating oil being around
The calculation works on the energy in a litre of ethanol being 23.4MJ.
(I do not know what price fuel ethanol sells for in Australia.)
The calculation works on the specific gravity of LPG being 0.52 and the energy
in a tonne of LPG being around 49.4GJ.
This calculation works on one megawatt hour of electricity being equal to
3.6GJ. In South Australia there is also a substantial supply charge for
electricity, and 10% goods and services tax. These can increase the effective
price that you pay for your electricity by 40% or more.
My source for the energy content of fossil fuels and ethanol
was the Australian Bureau of
Agricultural and Resource Economics (ABARE) document titled
Information on the energy content of firewood came from
Another source I used for the energy content of liquid fuels was
While petrol (automotive gasoline) is not used for heating,
the reader might be interested to know that, by volume, automotive diesel
contains 17% more energy than petrol. By weight petrol contains 2% more
energy than diesel.
On this page...
Calculate cost of energy from LPG
Calculate cost of energy from coal
Calculate cost of energy from electricity
Calculate cost of energy from firewood
Calculate cost of energy from oil